Heat sensitive transfer methods, electrophoto-graphic methods and ink jet methods are currently being actively studied as technology relating to color hard copy. Compared to other methods, heat sensitive transfer has many advantages due to the ease of maintenance and operation of equipment, and the low cost of equipment and expendable items.
Methods of heat sensitive transfer include a method whereby a heat transfer dye providing material comprising a heat fusible ink layer formed on a support is heated by a thermal head to melt the ink and record the image on a heat transfer image receiving material, and a method whereby a heat transfer dye providing material comprising a dye providing layer containing a thermomigrating dye formed on a support is heated by a thermal head or the like to transfer the dye to a heat transfer image receiving material. Since the latter transfer method using thermomigrating dyes makes it possible to vary the amount of dye transferred by altering the energy supplied to the thermal head, gradation recording is easy and it is particularly advantageous in making high quality full color records.
However, there are various restrictions on the thermomigrating dyes used in this method, and there are very few which satisfy all performance requirements.
The performance requirements include, for example, having desirable spectroscopic characteristics in color reproduction, being easy to sublimate and move through a medium using heat, being resistant to light and heat, being resistant to a variety of chemicals, not easily having sharpness reduced, the image not being easily re-transferable, being easily synthesizable, and being easy to prepare a heat sensitive transfer material. The development of a cyan dye satisfying these requirements has been particularly hoped for.
A variety of suggestions have been put forward for cyan dyes for use in heat transfer, and among these the indoaniline-based dyes disclosed in JP-A-61-268493, JP-A-62-191191 and JP-A-63-91287 have a relatively superior performance (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, the indoaniline dyes proposed so far suffer from the disadvantage that their light fastness is poor.
An object of the present invention is to provide a heat transfer dye providing material containing a cyan dye in which the above problem has been overcome.